Tag: cold stratification

My seeds of showy mountain ash (Sorbus decora), cold stratifying in the fridge, showed signs of germinating so I planted the little sproutlings in potting soil and put them in the coldest window, to delay their growth enough to allow the calendar to catch up to them. They are reaching for light a bit, but they are very cute.

Seeds of plants which grow in cool conditions may start to germinate in the fridge. Especially when I haven’t grown the species before, I may estimate that they need a much longer cold-moist stratification period than they do. It is useful to check on stratifying seeds — about once a month should do in the winter, more frequently as the season progresses.

I collected the showy mountain ash seeds in Nova Scotia this past September. I have very fond memories of this lovely shrub/small tree from a visit, some years ago, to Newfoundland in early October. Bright orange clusters of mountain ash fruit were everywhere, the most colourful thing in the landscape.

The magnificent scenery of coastal Newfoundland, with a fruiting showy mountain ash in the foreground.

I can now sit back and enjoy a cup of coffee, if not something a little stronger. (Although, the way Michael makes the double expresso, it is difficult to think of a stronger beverage.) I have sorted my seeds into those needing stratification and those not, and further sorted them by date that they need something done to them. All the seeds needing three months moist cold are now in their zip-top baggies in the fridge. The two native lilies that are hypogeal* germinators are in pots of soil, and the “challenging” species that need warm stratification before they need cold stratification are in baggies on top of the fridge.

Seed packets – mostly native wildflowers.

One species defies attempts to tame it: whorled milkweed. The sources I could track down on-line all implied it has to experience winter and this wussy fridge-time fakery won’t cut it. The whorled milkweed seeds are in a pot of medium in the fridge now. Next time we go to the farm, I will find a sheltered corner for it outside and cover the pot with snow and hope for the best.

Gardeners who do vegetables and annuals and perhaps a few of the easy-to-germinate perennials don’t do any of this. Planning the vegetables for a succession of crops and efficient use of garden space is its own art. I know because I do that as well.

Extraordinarily diverse, native perennials have seeds that will not germinate until they have been convinced they have been eaten by birds, planted by squirrels, abraded by waves, flung about by goldfinches, pooped out by racoons, and/or experienced winter. Providing cold, moist conditions to mimic winter is the single most important technique for germinating seeds of native plants.

It might seem daunting if you have never done it before. Once you have done it a few times, and found that it works like a charm, you will consider cold-moist just another pretreatment that you take in your stride. Nasturtiums germinate better and faster with an over-night soaking? Fine. Good. Done. Chances are, you still think nasturtiums are easy to grow. An easy cold-moist-treatment seed to start with is the lovely butterfly milkweed (Asclepias tuberosa). I got an extra packet of butterfly milkweed seeds from the Ontario Rock Garden Society Seed Exchange, as a bonus for contributing to the exchange. This year, lots of organization are handing out seeds of this species, to raise awareness for monarch butterfly conservation. You might have a packet yourself.

This is what you do:

Label a zip-top baggie with a waterproof marker:

Butterfly milkweed

C(90)

In cold: Feb 15 , out cold: May 15

Place a folder paper towel inside the baggie.

Put seeds into the fold of the paper towel.

Spritz or sprinkle some water onto the paper towel so that it is damp but not sodden. There should not be any liquid water in the bottom of the bag.

Close zip top. Place in fridge.

Take out on May 15th and sow the milkweed seeds.

Easy. (Sorry about the two Step1’s. I cannot make WordPress put a bulleted list inside a numbered list.)

Lots of folks prefer a little damp vermiculite to damp paper towel. If you have vermiculite on hand, go ahead and use it. The C(90) code comes from Prairie Moon Nursery and it is the most sensible code I have found. In cold for 90 days – C(90). Right.

Butterfly milkweed seed is large enough to be able to handle individually. When seed is very, very small or when it has fluffy bits, as a lot of, say, aster seed does, it clings to the paper towel and is a pain to remove when the time comes to sow it. Use the vermiculite method for these.

Butterfly milkweed is a warm season grower and it will not sprout prematurely in the fridge. With other species, this is a definite risk. Each species has its own chill requirements and quirks. There is always much to learn.

* Delayed double hypogeal germination: To be discussed, but not today.

After several years hiatus, I am again growing native wildflowers for restoration projects.

Pond this winter.

This year I have a farm pond restoration project. A pond that was dug about thirty-five years ago has become obscured by staghorn sumac to the point where it can no longer be seen, or even visited without a machete. Nothing much else native has come in to colonize it. The idea is to remove the sumac along most of the shore and replace it with diverse native vegetation.

Of course, the scope of the project grew during the winter, after seed collecting season had finished, so the species I am growing for this year are limited to those I happened to have plus a few I needed to buy, minus those that are too fussy to germinate. Once again my refrigerator is home to plastic baggies filled with damp paper towels, wherein seeds that require cold stratification are getting a cool, moist approximation to winter.

A species I have never grown before, Decodon verticillatus, seed purchased from Gardens North, is tiny, requires light to germinate, and needs three months cold stratification – according to the package, which in this case I will trust. Kristl Walek, the owner of Gardens North, is practical and experienced, and I have been able to find almost no other information on growing D. verticillatus. Thus, the seed had to be sown on top of a flat of damp potting soil, bagged up to keep it moist, and put in a refrigerator. I persuaded the client to put it in his refrigerator, so it is not taking up space in mine. (Note to self: do this more often.) Because I didn’t put in my Gardens North order until late February, the flat won’t come out into the warmth and light until June 1st. That’s fine. There is little point trying to push the growing season with natives, especially ones you don’t know well. Chances are seeds in the wild would not begin to germinate until the ground around them warmed thoroughly, perhaps in late May.

I am trying to think of the common name for Decodon verticillatus and the only name I can come up with is water-willow.

Seriously? Water-willow? The plant likes moist soil, has pretty purple-pink flowers all along its herbaceous stems, which arch and trail gracefully, making it perfect for planting at the edge of a pond. It is not at all related to the woody willow family of shrubs and trees. Perhaps it is the misleading common name which has prevented this plant from becoming popular. (Or perhaps it is just another example of the way North American horticulturists ignore North American plants.) I own a lot of books about gardening with native plants and I just got a whole bunch more books about ponds from the library, and none of them even mentions D. verticillatus.

Decodon verticillatus: Pelee Marsh

I first saw this pretty plant years ago in Pelee Marsh, and because I had seen it in the deep South and not elsewhere, I just assumed it was a Carolinian species. Then I saw it again, a lot of it, on a Field Botanists of Ontario trip to a wetland well north of Kingston, on the Frontenac axis. Range maps put water-willow growing well up into southern Quebec, so it is suited to my Zone 4b project. I don’t know why it is not seen more places. Perhaps it is one of those plants whose distribution is just mysteriously spotty and sporadic. Or perhaps the practice of managing water-levels in cottage country for boaters rather than the native inhabitants has eradicated water-willow from places it once grew. I am sure it is doing fine, deep into swamps and marshes, but it would be nice to see it from time to time from a canoe on a day paddle.